A document conveying apparatus such as a scanner includes components such as multiple rollers for conveying documents, and causes a driving force generation module such as a motor to drive each component. In general, in a document conveying apparatus, a single driving force generation module drives multiple components in order to suppress an increase in the electric power consumption. However, when a single driving force generation module is configured to drive multiple components, and drives only a particular component, the other components are driven at the same time, and therefore, it is not easy for a single driving force generation module to appropriately drive components of which uses are different.
A sheet feeding apparatus having a pickup roller, a feed roller disposed downstream of the pickup roller, and a retard roller brought into pressurized contact with the feed roller and configured to drive each roller with a single driving source has been disclosed. The retard roller includes a torque limiter, and when there is no sheet or when a single sheet is conveyed, the retard roller is driven and rotated in a sheet conveying direction, and when multiple overlapping sheets are conveyed, the retard roller rotates backward to separate the sheets. In this sheet feeding apparatus, when the retard roller rotates backward, and the feed roller is driven and rotated in a direction opposite to the sheet conveying direction, a planet gear is used so as not to transmit the rotation of the feed roller to the pickup roller (see Japanese Laid-open Patent Publication No. 2004-43146).
A feeding apparatus including a pick roller for picking up documents placed on a shooter, a separation roller located at a conveying downstream side of the pick roller and configured to separate and feed a document and a preceding feed roller and a subsequent feed roller for conveying the document is disclosed. This feeding apparatus further includes a pressurizing arm for pressurizing the documents placed on the shooter from above and a planet gear for controlling the movement of the pressurizing arm. In this feeding apparatus, the preceding feed roller, the subsequent feed roller, the separation roller, and the pick roller rotate in a document conveying direction in accordance with a normal rotation operation of a stepping motor, so that the documents placed on the shooter are picked up and the picked-up documents are separated and fed. When the stepping motor rotates forward with the planet gear, the pressurizing arm operates to pressurize the documents, and when the stepping motor rotates backward, the pressurizing arm operates so as not to pressurize the documents (see Japanese Laid-open Patent Publication No. 2001-233458).
A color printer including a feeding roller and a retard roller disposed so that its external periphery is in contact with an arc portion of the feeding roller is disclosed. In this color printer, a driving force is input into a feeding gear connected to a feeding roller and a retard gear connected to the retard roller via a transmission mechanism having a planet gear. In this transmission mechanism, when the motor rotates forward, the planet gear is meshed with the feeding gear, and the sheets are separated and conveyed, and when the motor rotates backward, the planet gear is detached from the feeding gear, and the sheets are conveyed by the retard roller (see Japanese Laid-open Patent Publication No. 2012-66936).